Hi,
I'm halfway through construction of a small coastal chalet - I am building it myself and it’s the first time I’ve done a project like this so I’m hoping this forum can help with gaps in my knowledge as I move from the “design on a page” to the reality of building it…
The construction is timber frame with a steel skeleton frame (there’s gale force winds in my location!). The steel columns in the corners are fixed to the concrete slab foundation; the timber frame inbetween the steels is built on 2x concrete blocks on the foundation (to keep DPC >150mm to ground level). The wall sole plate sits on the blocks and up tight to the steel column at each end, and the timber studwork is fixed to the steel beam. I’ve attached a very rough drawing.
The detail I’m stuck on is in the corners at the base of the steel column. The I-beam is 152x157 with a wider base plate attached to the foundations (base plate is ~300 sq). The concrete blocks are outside this base plate but the timber frame stud work and sole plate are butted up to the I-beam - leaving a gap under the sole plate in all of the corners - which is currently letting in the rain, and I fear in future will be a route in for rodents.
How should I fill this void? Should the timber frame OSB sheathing and external wall insulation extend down to the slab and I fill the void from the inside with insulating foam? That solution doesn’t seem rain proof… Or should I create a concrete post base around the steels, up to the height of the concrete blocks? This seems a much better way to weather proof the corners and prevent driving rain coming in but seems tricky in reality to do without getting in the way of the external wall insulation reaching down to the slab.
And a second question: On some of my walls, the OSB sheathing doesn’t sit up tight to the steel column - there is a gap of ~10mm because the timber frame stud work is wider than the steel I-beam. Outside the OSB will be external wall insulation boards, breathable membrane, cladding batons then timber cladding. Do I need to fill in these gaps on the inside of the OSB sheathing with insulating foam? The external wall insulation is to keep the steel within the warm side of the building - so I fear that quite large air gaps next to the steel will prevent the EWI from doing its job?
Sorry for the essay - and thanks so much for any help!
I'm halfway through construction of a small coastal chalet - I am building it myself and it’s the first time I’ve done a project like this so I’m hoping this forum can help with gaps in my knowledge as I move from the “design on a page” to the reality of building it…
The construction is timber frame with a steel skeleton frame (there’s gale force winds in my location!). The steel columns in the corners are fixed to the concrete slab foundation; the timber frame inbetween the steels is built on 2x concrete blocks on the foundation (to keep DPC >150mm to ground level). The wall sole plate sits on the blocks and up tight to the steel column at each end, and the timber studwork is fixed to the steel beam. I’ve attached a very rough drawing.
The detail I’m stuck on is in the corners at the base of the steel column. The I-beam is 152x157 with a wider base plate attached to the foundations (base plate is ~300 sq). The concrete blocks are outside this base plate but the timber frame stud work and sole plate are butted up to the I-beam - leaving a gap under the sole plate in all of the corners - which is currently letting in the rain, and I fear in future will be a route in for rodents.
How should I fill this void? Should the timber frame OSB sheathing and external wall insulation extend down to the slab and I fill the void from the inside with insulating foam? That solution doesn’t seem rain proof… Or should I create a concrete post base around the steels, up to the height of the concrete blocks? This seems a much better way to weather proof the corners and prevent driving rain coming in but seems tricky in reality to do without getting in the way of the external wall insulation reaching down to the slab.
And a second question: On some of my walls, the OSB sheathing doesn’t sit up tight to the steel column - there is a gap of ~10mm because the timber frame stud work is wider than the steel I-beam. Outside the OSB will be external wall insulation boards, breathable membrane, cladding batons then timber cladding. Do I need to fill in these gaps on the inside of the OSB sheathing with insulating foam? The external wall insulation is to keep the steel within the warm side of the building - so I fear that quite large air gaps next to the steel will prevent the EWI from doing its job?
Sorry for the essay - and thanks so much for any help!
